T-Mobile started letting customers route calls through Wi-Fi way back in 2007. And now that Verizon has added the feature, every member of the Big Four provides some form of Wi-Fi calling on some phones. A few smaller carriers, including Republic Wireless and Google’s Project Fi, are championing a “Wi-Fi first” model that routes as much cellular use through Wi-Fi as possible.

Wi-Fi calling will soon be an important part of mobile service, and it can save some customers big money.

What is Wi-Fi calling?

It’s exactly what it sounds like.

When you place a Wi-Fi call, it’s picked up by your current Wi-Fi network, instead of a nearby cell tower. If you have the feature enabled on your phone, any call you make should be routed through Wi-Fi automatically; there’s no special button to press or program to use.

The advantages of Wi-Fi calling

For customers, Wi-Fi calling can mean better service in places where it’s usually spotty, such as rural areas, certain buildings and basements. It can be a plus for international travelers, as most carriers allow free Wi-Fi calling and texting back to the U.S. with no pricey roaming charges.

For carriers, it means a reduced load on their network hardware.

For these reasons, Lynnette Luna, an industry analyst with Current Analysis, says Wi-Fi will become an integral part of future cellular coverage. “We will see Wi-Fi be just another part of the 5G network as users seamlessly move in between the two,” she says. “That may also happen in the 4G world down the road.”

‘Wi-Fi first’

Some smaller carriers are leveraging Wi-Fi calling to save their customers money. So-called “Wi-Fi first” carriers like Republic Wireless and Google’s Project Fi keep customers on Wi-Fi for as long as possible, falling back on cell towers only when absolutely necessary.

The transition is meant to be seamless, but customers sometimes complain about dropped called during the switch.

Project Fi was only recently released to the public, but Republic Wireless has been doing Wi-Fi first since 2011. The company inspires passion: Republic took first place out of 13 prepaid carriers in a recent Consumer Reports customer satisfaction survey.

James Boggs, a Republic customer of two years in Fowler, Ohio, switched to the carrier from Verizon. “[Verizon] had amazing service, but when your bill hits $300 a month for five lines, and data is extra, it’s time to switch,” he says.

Verizon’s service was great, Boggs adds, in all but one place: his house. “I can actually make phone calls inside my house again with Wi-Fi calling,” he says.

Boggs says he now pays around $12 per month for a single line on Republic. The company says its average customer pays $13.83 per month.

The drawbacks

Wi-Fi-first calling isn’t for everyone, though. In addition to complaints that calls are dropped when transitioning from Wi-Fi to cellular, not all users find that Wi-Fi call quality is better. Some users report delays in conversations conducted over Wi-Fi, and call quality may also suffer if many people are piling on to the same hotspot.

Heavy data users and frequent streamers are better off with other arrangements as well.

Republic and Project Fi have similar pricing structures, in which customers pay a low monthly rate for unlimited talk and text and a flat rate for only the data they use. (If you don’t use all your data in a month, you’re refunded the balance.) Republic costs $10 per month, with data at $15 per gigabyte. That’s unlimited talk and text with 1GB of data for $25 per month. No other prepaid carrier comes close. However, if you use 4GB of data per month, Republic will cost you $70. The same amount of data costs $40 per month from Virgin Mobile.

Both carriers come with limited phone selection as well, though Republic Wireless is upping its roster from two Android phones to 11 this month. Project Fi currently allows only the Nexus 5X and the Nexus 6P.

Is Wi-Fi calling right for you?

If you’re already on a Big Four carrier and don’t get good service in your home or office, put your router to work. Contact your carrier to find out whether Wi-Fi calling can be activated on your phone.

If price is your biggest consideration when choosing a cell plan and you’re not a heavy data user, Wi-Fi-first carriers are definitely worth a look — as long as you’re OK with a limited phone selection and some potential technological hiccups.